I am so sorry everyone for my delay in answering questions... I have been working for a whole week on testing and checking my PCB... discovering that the CD4011 by NXP did not function with this PCB. The problem has been solved after I bought a ST.

Sorry for the delay in reply here too.
Nice looking builds! I thought you had the Ringmod in there as well, hence why i figured it was a tight build. Plenty of room here, great.

Just figured acrylic panels perhaps wouldnt be a bad idea. To avoid the locking between the VCO's especially.
Or - have you guys solved this in any other way?
It gets a bit disturbing at times when you DONT want sync to happen.

furio wrote:

I am so sorry everyone for my delay in answering questions... I have been working for a whole week on testing and checking my PCB... discovering that the CD4011 by NXP did not function with this PCB. The problem has been solved after I bought a ST.

Thanks for the info about the CD4011 issue.
I am testing a separate board for waveshaper, ringmod and subosc.
I will share the layout when the testing will be finished.
I have built only one VCO and the only issue I noticed is when I put it in my grounded rack the VCO is detuned.

I breadboarded the VCO some months ago, and tried a bunch of transistors. I fond that the 2N alternatives delivered the american raw ARP sound, while the BC ones made it more in to the realms of round Roland.
So, i wouldnt say it improves the sound, rather gives it a different tone.

I breadboarded the VCO some months ago, and tried a bunch of transistors. I fond that the 2N alternatives delivered the american raw ARP sound, while the BC ones made it more in to the realms of round Roland.
So, i wouldnt say it improves the sound, rather gives it a different tone.

Hi steffensen,
I've noticed a marked improvement of the operation, rather than a difference in tone = the instrument results is more convincing to me.
In theory, the transistors 2N3904 and 2N3906 should be tended to more audiophile sound... I guess it's just a matter of thermal coupling and perhaps a work of this kind one might approach a similar result (photo).

I tried to make two adapter's with the recommended transistors & better tempcos = after comparing, the VCO with 2N3904/2N3906 expo converter seems to malfunction.
For years I used the dual version PCB by Andy and it was my favorite module... perhaps I would install two BC847BPN's also on them.
The tone changes a lot more by replacing the 2N5910 with a 2N3906... however, for a while I try the VCO with the 2N3906 instead the 2N5910, but I have no intention to replace the 2N5459's.
It disturbs me a lot more to run a celluar phone in standby mode in the studio for the damages arising in tone and operation, than the BC847BPN.
In any case, I like the Andy's idea to separate the dual VCO in individual modules. The single VCO improves drastically in sound and operation.

P.S. unfortunately I just destroyed my natural ADC and I have to fix it... I recorded with an ADC with integrated Pre-amplifier on which they are installed an array of AD8620's, these inject too much violence and obscure the detail.

Hi steffensen,
I've noticed a marked improvement of the operation, rather than a difference in tone = the instrument results is more convincing to me.
In theory, the transistors 2N3904 and 2N3906 should be tended to more audiophile sound... I guess it's just a matter of thermal coupling and perhaps a work of this kind one might approach a similar result (photo).

I tried to make two adapter's with the recommended transistors & better tempcos = after comparing, the VCO with 2N3904/2N3906 expo converter seems to malfunction.
For years I used the dual version PCB by Andy and it was my favorite module... perhaps I would install two BC847BPN's also on them.
The tone changes a lot more by replacing the 2N5910 with a 2N3906... however, for a while I try the VCO with the 2N3906 instead the 2N5910, but I have no intention to replace the 2N5459's.
It disturbs me a lot more to run a celluar phone in standby mode in the studio for the damages arising in tone and operation, than the BC847BPN.
In any case, I like the Andy's idea to separate the dual VCO in individual modules. The single VCO improves drastically in sound and operation.

Interesting.
I didnt do anything particular to my 2N3904/2N3906 expo converter, it just works great. I use a 1.87 tempco, which might have something to do with that tho.
What do you mean by operation? Is FM behaving better? Or something else?
I havent found a 2N5910 yet, but i think i have some on the way now (just hope they arent fakes).
I did however (for the 2N5910) try comparing the 2N3906 with the later used by ARP: 2N4125.
Made no difference in sound at all, but perhaps the latter one dont get heated as much. I didnt measure.
Using BF245 instead of the 2N5459 however made a difference for sure. (more in to the Roland realm i described above)

As said, mine is working great BUT the locking/syncing of the VCO's is disturbing. Its one thing if i have chose to use Sync, but if i havent i dont want it to happen. And there is no way to stop the Ground joining up thru the panel obviously.
This should be a problem with the original Odyssey as well imo, wonder how they solved that.. if this is the answer to stop the locking.

I cant be the only one experiencing this and wanting to find a solution?

I too believed for three years that my dual VCO was great... Though now it just works better... by giving a close ear I would say that the auto-sync could still be improved (I do not know how I should proceed to investigate technically and/or whether I have the suitable lab equipment... I only have a pocket oscilloscope with which I can almost see nothing).

I think you could use Nomex paper for insulating the panel from the ground board trace as an easy solution ( or you can use Furio's acrylic panels).
Thanks a lot for sharing all your experiments with this VCO board, this threat is getting hot.

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot vote in polls in this forumYou cannot attach files in this forumYou can download files in this forum

Please support our site. If you click through and buy from our affiliate partners, we earn a small commission.